Revert "Make `asyncio.sleep(0)` run faster (#4568)" (#4583)

docs/project/changelog.md

@@ -54,9 +54,6 @@ myst:
 - {{ Enhancement }} Fixed a memory leak when iterating over a PyProxy.
   {pr}`4546`
 
-- {{ Enhancement }} `asyncio.sleep(0)` now runs the next task a lot faster.
-  {pr}`4568`
-
 - {{ Fix }} `pyodide.mountNativeFS` will no longer silently overwrite an
   existing nonempty directory. Also it throws much clearer error messages when
   it fails.

pyproject.toml

@@ -31,7 +31,6 @@ module = [
   "matplotlib.*",
   "PIL.*",
   "pyodide_js",
-  "pyodide_js._api",
   "pytest_pyodide",
   "pytest_pyodide.runner",
   "pytest_pyodide.utils",

src/js/api.ts

@@ -8,7 +8,6 @@ import { type PyProxy, type PyDict } from "generated/pyproxy";
 import { loadBinaryFile, nodeFSMod } from "./compat";
 import { version } from "./version";
 import { setStdin, setStdout, setStderr } from "./streams";
-import { scheduleCallback } from "./scheduler";
 import { TypedArray } from "./types";
 import { IN_NODE } from "./environments";
 
@@ -52,10 +51,6 @@ API.saveState = () => API.pyodide_py._state.save_state();
 /** @private */
 API.restoreState = (state: any) => API.pyodide_py._state.restore_state(state);
 
-// Used in webloop
-/** @private */
-API.scheduleCallback = scheduleCallback;
-
 function ensureMountPathExists(path: string): void {
   Module.FS.mkdirTree(path);
   const { node } = Module.FS.lookupPath(path, {

src/js/package.json

@@ -81,7 +81,7 @@
   "scripts": {
     "build": "tsc --noEmit && node esbuild.config.mjs",
     "test": "npm-run-all test:*",
-    "test:unit": "cross-env TEST_NODE=1 ts-mocha --exit --node-option=experimental-loader=./test/loader.mjs --node-option=experimental-wasm-stack-switching -p tsconfig.test.json test/unit/**/*.test.*",
+    "test:unit": "cross-env TEST_NODE=1 ts-mocha --node-option=experimental-loader=./test/loader.mjs --node-option=experimental-wasm-stack-switching -p tsconfig.test.json test/unit/**/*.test.*",
     "test:node": "cross-env TEST_NODE=1 mocha test/integration/**/*.test.js",
     "test:browser": "mocha test/integration/**/*.test.js",
     "tsc": "tsc --noEmit",

src/js/scheduler.ts

@@ -1,19 +0,0 @@
-/**
- * Schedule a callback. Supports both immediate and delayed callbacks.
- * @param callback The callback to be scheduled
- * @param timeout The delay in milliseconds before the callback is called
- */
-export function scheduleCallback(callback: () => void, timeout: number = 0) {
-  // In modern browsers, setTimeout has throttling minimum delay (mostly 4ms).
-  // So to support immediate callbacks, we use MessageChannel if the delay is less than 4ms.
-  // Ref0: https://github.com/pyodide/pyodide/issues/4006
-  // Ref1: (firefox) https://developer.mozilla.org/en-US/docs/Web/API/setTimeout
-  // Ref2: (chrome) https://developer.chrome.com/blog/timer-throttling-in-chrome-88
-  if (timeout < 4) {
-    const channel = new MessageChannel();
-    channel.port1.onmessage = () => callback();
-    channel.port2.postMessage("");
-  } else {
-    setTimeout(callback, timeout);
-  }
-}

src/js/test/unit/scheduler.test.ts

@@ -1,21 +0,0 @@
-import * as chai from "chai";
-import { scheduleCallback } from "../../scheduler";
-
-describe("scheduleCallback", () => {
-  // Note: This test requires `--exit` flag to be set for mocha
-  //       to avoid hanging the process
-  //       see: https://github.com/facebook/react/issues/26608
-  it("should call the callback immediately if timeout is 0", () => {
-    const start = Date.now();
-    scheduleCallback(() => {
-      chai.assert.isAtMost(Date.now() - start, 4);
-    });
-  });
-
-  it("should call the callback after the given timeout", () => {
-    const start = Date.now();
-    scheduleCallback(() => {
-      chai.assert.isAtLeast(Date.now() - start, 10);
-    }, 10);
-  });
-});

src/js/types.ts

@@ -322,7 +322,6 @@ export interface API {
   runPythonInternal_dict: any;
   saveState: () => any;
   restoreState: (state: any) => void;
-  scheduleCallback: (callback: () => void, timeout: number) => void;
 
   package_loader: any;
   importlib: any;

src/py/pyodide/webloop.py

@@ -11,7 +11,7 @@ from typing import Any, TypeVar, overload
 from .ffi import IN_BROWSER, create_once_callable
 
 if IN_BROWSER:
-    from pyodide_js._api import scheduleCallback
+    from js import setTimeout
 
 T = TypeVar("T")
 S = TypeVar("S")
@@ -343,10 +343,7 @@ class WebLoop(asyncio.AbstractEventLoop):
                 else:
                     raise
 
-        scheduleCallback(
-            create_once_callable(run_handle, _may_syncify=True), delay * 1000
-        )
-
+        setTimeout(create_once_callable(run_handle, _may_syncify=True), delay * 1000)
         return h
 
     def _decrement_in_progress(self, *args):

src/tests/test_webloop.py

@@ -497,20 +497,3 @@ async def test_inprogress(selenium):
         loop._no_in_progress_handler = None
         loop._keyboard_interrupt_handler = None
         loop._system_exit_handler = None
-
-
-@run_in_pyodide
-async def test_zero_timeout(selenium):
-    import asyncio
-    import time
-
-    now = time.time()
-
-    for _ in range(1000):
-        await asyncio.sleep(0)
-
-    done = time.time()
-    elapsed = done - now
-
-    # Very rough check, we hope it's less than 4s (1000 * 4ms [setTimeout delay in most browsers])
-    assert elapsed < 4, f"elapsed: {elapsed}s"